Things to keep in mind : Raven is a mobile class, with lowest HP and Def in game. A bit more Mdef than Def, but still very low. You have one goal : deliver as much damage as you can, and not get hit.

Raven is a AGI and STR hybrid : Either pump everything into Agi, or Agi until the Crit cap, and then some STR. (It's advised to have both agi and str plates no matter what build you go for. You do not need def / health plates. Your job is not to get hit)
[You still need 1,5M HP at L90 cap]

Skills to go for :
Assasin skill tree :
- All yellow skills. Minus leap.
- Any attacking skill (I prefer Shadow Hand, and Edged fan) until you reac 45 points in assasin tree. (Important! You must put one point in Triple edge and Raid.)

And that's it.
All you do is mash your skills in random order, while avoiding getting hit. Be sure to learn using Air recover and doge skills to their max potential.
If you get light on fire, poisoned, or your HP falls bellow 70% (you got hit by anything) - use Dedicated Shadow and avoid repeating the mistake.